LEDs are everywhere. Basics of LED application fields

0 Introduction

LED is the abbreviation of Light Emitting Diode, which is the third generation of solid-state lighting source after incandescent lamps and fluorescent lamps . In terms of internal structure, LED has P region and N region similar to semiconductor diodes, forming a "PN junction".

When current flows, electrons are pushed to the P region, where they recombine with holes and emit energy in the form of photons. This is the principle of LED light emission. Since the birth of the first LED in the 1960s, this new light source with small size, long life, energy saving and environmental protection has entered people's lives. Now, from indoor lighting to urban landscape lighting, from instrument indicators to car lights, from televisions to large-screen displays, LEDs are everywhere and are changing people's lives. Below, I will briefly talk about the impact of LEDs on modern human life in terms of lighting and display.

1 Application of LED in urban lighting

Urban functional city lighting is an indispensable condition to ensure people's work and life; urban landscape lighting can beautify the city, bring vitality and vigor to the city, enhance the city's image, enrich people's lives, and provide convenience for people's work and life.

At present, the existing public lighting equipment mainly includes sodium lamps, metal halide lamps and mercury lamps, which have low photoelectric conversion efficiency and consume a lot of electricity. In today's global energy shortage environment, energy conservation has become a general trend, and green, efficient and long-life LED street lights are gradually coming into people's view. LED street lights have the following advantages: high luminous efficiency, low reflection loss of lamps , and 70% energy saving; with digital brightness control function, it is more energy-saving; no high voltage is required, and it is highly safe; with software, the brightness can be automatically controlled remotely; it provides ultra-high brightness and high color rendering lighting sources in special circumstances such as accidents, foggy days, and rainy days; it is easy to install and maintain; module installation, no redundant wiring; it will not cause light pollution or waste; long life means that it does not need to be replaced frequently, thereby reducing the potential for traffic interruption and the maintenance costs paid for it.

2 Application of LED in Automotive Lighting

Automotive light sources play an extremely important role in the lighting field, and their output accounts for about 10% of the total output of lighting sources. LEDs were first used in automotive lighting in the mid-1980s, when they were mainly used for high-mounted brake lights. Compared with traditional incandescent lamps, LED brake lights can operate at a lower drive current, and lower power can reduce the volume and weight of the car's internal wiring system. LED brake lights have a short response time. If the car in front brakes immediately, the car behind will see the signal 0.7s~1s earlier than with traditional incandescent brake lights, which leaves more reaction time for the driver, thereby improving driving safety.

At present, automotive LEDs can be divided into those used externally and internally. The internal ones include the instrument panel, air conditioner, audio indicator lights, and internal reading lights; the external ones include brake lights, tail lights, turn signals, side lights, etc. As the optical performance of LEDs continues to improve, the packaging design will be more targeted and practical, which will provide greater development space for the personalized and integrated design of automobiles. With the rapid development of technology, the price of LEDs has been continuously decreasing, and the reduction will be even greater in the future, so the use of LEDs in automobiles will become more and more popular.

3 Application of LED in Home Lighting

Since ancient times, human beings have been pursuing light, and the development of human civilization is closely related to the progress of lighting technology. Home lighting has become a highlight of modern living environment, playing a role in beautifying and improving the quality of life. Home lighting requires light sources to ensure that the working, learning and living environments meet comfortable illumination standards and good lighting quality, objectively display the brightness and color of objects, and obtain the real effect of human eyes directly observing external scenery. While having high luminous efficiency and sufficient brightness, it should also have a color temperature close to natural light and a high color rendering index. When LED is used for indoor lighting, the lighting source can be adjusted to make the indoor light change with the time of morning, noon and night, so that the indoor light environment is close to natural light such as the moon, stars and sun. It can be said that the entry of LED into indoor lighting is the most important milestone for semiconductor lighting to enter the general lighting market. In the near future, the indoor lighting of thousands of households will be the market of LED.

4 Application of LED in backlight

Backlight is the light source provided to the LCD panel, mainly composed of light source light guide plate, optical film, plastic frame, etc. LED as the backlight of display screen is the most widely used field of LED, accounting for about 40% of LED applications, such as the backlight of mobile phones and laptops. At present, LED backlight has entered the LCD TV.

First, compared with the cold cathode fluorescent tubes on traditional display devices, LCD TVs that use LED as backlight can improve viewing quality, especially color saturation. Secondly, because of the flat light source characteristics of LED, LED backlight can also achieve regional color and chromaticity adjustment functions that cold cathode fluorescent tubes cannot match, thereby achieving more accurate color reproduction. Thirdly, in terms of luminous life, LED backlight technology surpasses cold cathode fluorescent tubes. The life of ordinary cold cathode fluorescent tube backlight is basically around 30,000 hours to 40,000 hours, while the current life of white LED backlight is as high as 100,000 hours.

With the promotion of environmental certification in the world, cold cathode fluorescent lamps containing lead and mercury have been gradually abandoned. In addition, with the breakthrough increase in LED brightness and the reduction in production costs in recent years, the prospect of LED backlight is very good. People will also enjoy more and more comfort in terms of environmental protection, ultra-thinness, high image quality, etc.

5 Application of LED in display screen

The development of modern information display technology has formed a series of information display products such as CRT, LCD, plasma display, LED, etc. With the improvement of LED material technology and process level, large-screen LED intelligent display screens that integrate light and electricity using computer control have been applied to many fields.

LED display screens are divided into graphic display screens and video display screens, both of which are composed of LED matrix blocks. Graphic display screens can display Chinese characters, English text and graphics synchronously with computers; video display screens are controlled by microcomputers, with graphics, text and images, playing various information in a real-time, synchronous and clear information transmission method, and can also display two-dimensional, three-dimensional animations, videos, TV, VCD programs and live events. Compared with traditional screen display products, LED display screens have bright colors, strong three-dimensional sense, clear and delicate pictures, and good compatibility with computers. They are widely used in public places such as airports, stations, shopping malls, hospitals, hotels, banks, securities markets, and construction markets.

6 Conclusion

In addition, LEDs are also used in traffic signals, various electronic toys, instrument displays, various special lighting and other fields, penetrating into every aspect of modern life. We believe that with the development of LED technology and the reduction of prices, LEDs will enter thousands of households, saving precious energy for mankind and contributing to the protection of human living environment.